Electric heater



Dec. 15, 1942. J. ISBISTER ELECTRIC HEKTER Filed se i. 24, 1940 2 Sheets-Sheet l INVENTOR 'JJ/HL far/2e; fsbwfer WMifgi Ya Dec. 15, 1942 J. ISBISTER ELECTRIC BEATER Filed Sept. 24, 1940 2 Shets-Sheet 2 INVENTORV labiaer l J J L L Ja'mea' 9/72 A TTORNEY$ Patented Dec. 15, 1942 ELECTRIC HEATER James Isbister, Detroit, Mich, assignor to Dr. M. Webster Prince, Detroit, Mich.

Application September 24, 1940, Serial No. 358,158 In Canada September 25, 1939 3 Claims.

The present invention relates to electric heating units, and in particular provides such units, characterized as being extremely simple in construction, economical of manufacture, and efiicient in operation.

The principal objects of the invention are to provide an electric heating unit of the general type embodying one or more electric heating elements supported in predetermined relation to a hearth member, particularly characterized as embodying an improved construction of hearth, which in one embodiment takes the form of a pair of spaced apart insulating members having an insulating air pocket between them, and which, in another embodiment, takes the form of a heat reflecting surface; to provide such constructions wherein the heating elements are suspended from the hearth in an improved manner; to provide such constructions wherein the hearth and the heating elements are readily bodily removable as a whole from the burner surface of an associated stove or other supporting structure; to provide such constructions embodying improved terminal supports for the heating elements; and to generally improve the construction and arrangement of heating units of the above-indicated character.

With the above, as well as more specific objects in view, preferred but illustrative embodiments of the invention are shown in the attached drawings, throughout which corresponding reference characters are utilized to designate corresponding parts, and in which:

Figure 1 is a view in top plan of one embodiment of the invention;

Fig. 2 is a fragmentary view in vertical section, taken along the line 2-2 of Fig. 1;

Fig. 3 is a view in vertical section, taken along the line 33 of Fig. 1;

Fig. 3A is a fragmentary view of a modification of the arrangement of Figs. 1, 2 and 3;

Fig. 4 is an exploded view in perspective, showing the construction and arrangement of the terminal supports for the heating elements;

Fig. 5 is a view in top plan of another embodiment of the invention;

Fig. 6 is a fragmentary view in vertical section, taken along the line 65 of Fig. 5;

Fig. 7 is a view in vertical section, taken along the line 1-1 of Fig. 5;

Fig. 8 is a view in perspective of a modified terminal support which may be used in the embodiment of Figs. 5, 6 and 7;

Fig. 9 is a view in perspective of a wire terminal which may be employedin connection with the terminal support of Fig. 8; and,

Fig. 10 is a view in section of a modified embodiment of the invention.

The embodiment of the invention shown in Figs. 1 through 4 corresponds generally to the construction described in applicants United States application Serial No. 276,384, filed May 29, 1939, but distinguishes therefrom in respect to the supporting connection between the heating unit, the grille associated therewith, and the associated burner-surface or other supporting structure, and also in respect to the disposition of the interconnections between the individual heating elements and the external supply circuit.

Referring to Figs. 1 through 4, the heating unit comprises, generally, a plurality of heating elements 20, formed of suitable resistance wire, which are supported in parallel spaced relation to each other above a hearth formed of two spaced members 22 and 24. The just-identified elements are received in a suitable shell 26, the upper portion of which extends above the level of the hearth members 22 and 24, so as to define a substantially open topped heating chamber. In accordance with the present invention, the upper edge of the shell 26 is provided with a flange 21, which extends entirely therearound and rests upon a cooperating flange 28, which is provided with an escutcheon member 29 associated with the burner surface 30. The flanges 21 and Z8 serve to support the marginal edge of a conventional grille 3 I, which is positioned above and in spaced relation to the heating elements 20 and constitutes a supporting or work surface upon which the object to be heated may rest. The grille 3| may take any suitable form, but is illustrated as being of generally diamond-like form. The grille and the shell, which are readily separable from each other, are, therefore, freely suspended from the escutcheon 29 and are readily removable from the supporting structure represented by the surface 30.

As an alternative to the just-described arrangement, the arrangement of Fig. 3--A may be used, wherein the escutcheon 29a is provided with two shoulders 28a and 28b, to receive, respectively, the flange 21 of the shell and the edge of the grille 3 I.

The individual heating elements 20, four of which are shown by way of illustration, are each of elongated helical form, and are supported throughout their length upon rods 32 formed of insulating material. The rods 32 are each supported at each end thereof upon the terminals 33.

Each terminal 33 comprises an enlarged head 34 and a reduced shank portion 35, which is adapted to project through registering openings provided therefor in the hearth member 22. Each terminal 33 is also provided with an axially extending bore, which freely but snugly receives a mounting stud 36, and each head portion is also provided at one side with a shoulder 38, which forms a seat for the corresponding wire terminal 40.

Each wire terminal 40 is notched so that it may embrace the stud 36 and is also provided with a seat 42 to support the end of the insulating rod 32.

' Each mounting stud 36 passes through the bore in the corresponding terminal 33, as previously mentioned, and is provided at its lower end with one or more spacing washers, such as 44, 46 and 48, which spacing washers act to maintain the proper spacing between the upper and lower hearth members 22 and 24, respectively, as more clearly appears in Figs. 2 and 3. Also, in the present arrangement, the bus bars. such as 50, which are employed to interconnect the individual heating elements, and to form interconnections between such heating elements and the terminals 52 associated with the external supply circuit, are interposed between the hearth members 22 and 24, and are held in place by the mounting studs 36.

It is to be understood, accordingly, that the individual heating elements are assembled as a unit, with the upper hearth member 22, and that this unit directly rests upon the lower hearth member 24. The lower hearth member 24 in turn rests upon and is supported by an inwardly turned flange 54 formed at the bottom of the shell 28.

The wires, such as 56 (Fig. 3). which lead to the supply circuit, are usually provided with suflicient slack, so that, the entire heating structure can be lifted bodily from the escutcheon 29 for inspection or other purposes. Similarly, the grille 3| may be freely removed, after which the assembly comprising the upper hearth member 22' and the heating elements may be lifted out of the shell during which movement the lead wires, such as 56, are drawn into and pulled through the shell opening 58 provided therefor, thus affording easy access to the bus bar connections, and making it readily possible to loosen any of the mounting studs 36 and replace one or more of the heating elements 20, if desired.

In the modified embodiment of the invention shown in Figs. 5, 6 and 7, the improved heating unit comprises a plurality of heating units l0, each of helical form, which as in the previous instance, are provided (with supporting rods 12 formed of insulating material and which are suspended in spaced relation above a hearth constituted by the cup-like shell 14, the inner surfaces of the base and side walls whereof are suitablly polished or otherwise finished so as to provide efficient reflecting surfaces whereby the heat developed by the heating elements is either radiated directly upwardly therefrom. or is reflected upwardly from the just-mentioned reflecting surfaces.

As in the previous instance. the upper marginal edge of the shell 14 is provided with an outwardly projecting flange 16, which extends continuously therearound and which is adapted to seat upon a corresponding inwardly directed flange 18 associated with an escutcheon 80.

The escutcheon in turn rests directly upon and is supported by the associated burner surface 82. In this instance, also, the grille 8a is dimensioned to fit relatively snugly but freely Within the escutcheon 89 and the under-surface thereof rests upon the previously mentioned flange 76. With this relation, it will be appreciated that the entire heating unit comprises the shell M, the heating elements supported thereby, and the grille 84 may be freely removed from the burner surface as a unit. Also, the grille 84 may be independently removed from the heating unit so as to afford ready access to the interior of the shell 14.

In the embodiment now being described, the heating element 10 and the insulating rod 12 associated therewith are suspended within the shell 14 by means of a pair of identical insulating terminal supports 85 and 88, each whereof is of arcuate form and of a radius of curvature conforming to the radius of curvature of the shell 14. As clearly appears in Fig. 5, the insulating support 85 is positioned adjacent one side of the shell 14 and the support 88 is positioned in diametrically opposite relation, with the heating elements 10 and the rods 12 extending between them. The insulating support 88, as most clearly appears in Fig. '7. is provided with a plurality of recessed seats 90, one whereof is individual to each heating element, and a corresponding plurality of rod supporting notches 92, one whereof is individual to each insulating rod I2. The notches open into the just-mentioned seats, so that, as clearly appears in the drawings, when the free end of a particular insulating rod 12 is seated within its associated notch 92, the end of the corresponding heating element 10 is presented to the seat 90. Such end of the heating element is secured in place relative to the insulating support by means of a stud 90, which passes through the insulating support 88 and is secured in place by means of a nut 98 or equivalent element.

The underside of the insulating support 88 is provided with a plurality of counterbored portions 98. one whereof is individual to each heating element, and each counter-bore receives an axial projection such as I00, associated with a corresponding insulating spacer member I02. The just-mentioned projection N10 is passed through an opening provided therefor in the base of the shell 14, so that an effective interlock is thus provided to properly position the insulating support 88 relative to the shell.

In accordance with the arrangement disclosed in the above-identified patent, it is preferred to position the bus bars, such as l04, which are employed to form the inter-connections between the individual heating elements, in spaced relation beneath the shell 14, so as to afford easy access thereto. Accordingly, such bus bars are clamped between the previously mentioned insulating spacer member I02 and the previously mentioned holding nut 96.

It will be understood that the construction and arrangement of the companion insulating member 85, as well as the manner in which it is connected to the shell 14 and to the heating elements. conforms to the description just given with reference to the supporting member 82.

In order to form the connection between the previously mentioned bar I04 and the external supply circuit, it is preferred to employ the terminal assembly most clearly shown in Fig. '7, as comprising a stud 106, which is secured in place relative to the shell I4 by means of insulating spacer members I06 and H0, which interlock with the shell in the manner described with referenceto the spacer I02 and the insulating support 88. The bus bar, such as I04, is electrically connected to the stud I06, and is held in place relative thereto by clamping the same between the spacers H and the insulating washer I I2. The terminal I06 is provided with one or more clamping nuts I I4, which retain the insulated members I08, II 0 and I I2 in place thereon and which also serve to hold the terminal H6 in place.

In Figs. 5, 6 and '7, the bared ends of the respective heating elements III are directly clamped beneath the nlarged heads, such as 94a of the associated studs 94. In certain instances, it is found desirable to provide the ends of each heating element with preformed terminal members, such as the terminal members I20 of Fig. 9, and in such instances, it is preferred to use the insulating support I2I of Fig. 8 in preference to the previously described insulating supports 86 and 88.

As clearly appears in Fig. 9, the terminal I20 is provided with a stud engaging portion I22, which is notched to freely embrace the associated stud, such as 94, and is also provided with a back portion I24 provided with a projection I26, which is adapted to be bent under and clamped upon the end of the heating elements I0. It will be understood that the just-mentioned connection may be soldered or otherwise made more secure, if desired.

It is desirable that the insulating supports be so formed that a heating element may be replaced without entirely withdrawing the corresponding stud, such as 94, from the insulating supports and when employing terminals, such as the terminal I20, it is preferred to make the terminal receiving seats I28 of the insulating supports I2I of sufficient width so that, when the head of the corresponding stud, such as 94, is lifted slightly, the terminal I 20 may be slid thereunder and thereafter turned into proper position. Accordingly, in the construction of Fig. 8, the notches I20 and the openings I32 are displaced from the centers of the seats I 28. In all other respects, except those just noted, the construction and arrangement of the insulating supports I 2I may and preferably does conform to the description given above with reference to supports 86 and 88.

In the arrangement of Fig. 10, the previously described insulating supports, such as 86 and 88,

are replaced by a continuous ring-like insulating support I 40, which is provided with a plurality of seats, such as I42, notches I44 and axial openings to receive the heating element terminals I0, the insulating rods 12, and the mounting studs I46, respectively, in the previously described manner. In addition, the ring-like member I40 is provided with a plurality of openings, which are adapted to receive the studs I48 whereby the individual heating elements are connected to the external circuit. The latter openings are preferably provided with counterbored portions I50, whereby the associated connecting studs (not shown) may be recessed into the body of the insulating ring.

In addition. the arrangement of Fig. employs a covering ring I52, which directly rests upon the ring I40 and not only serves the purpose of concealing the otherwise exposed heads of the terminal studs I46, but also aids in insulating such studs from the surrounding shell, grille, and escutcheon parts. The underside of the covering ring I52 is provided with recessed pockets I54, so as to accommodate the heads of the mounting studs and so as to also accommodate thewire terminals, such as I56, which terminals correspond, for example, to terminals I20 of Fig. 9.

In all otherrespects, except those noted, it will be observed that the construction and arrangement of Fig. 10 conforms to that of Figs. 5, 6 and 7.

It will be appreciated from the foregoing that the present invention provides extremely simple construction for electric heating units, and it will be understood that although only several specific embodiments of the invention have been described, various further modifications in the form, number and arrangement of parts may be made without departing from the spirit and scope of the invention.

What is claimed is:

1. In an electric heating unit, the combination of a plurality of helically wound heating elements, an insulating rod individual to each said heating element, said insulating rods being passed axially through the corresponding heating lements, means for supporting said rods and elements so that said elements lie in a generally horizontal plane with the individual elements arranged substantially parallel to but laterally spaced from each other, said supporting means comprising a continuous ringlike insulating member common to all said heating elements and rods, said supporting member having two series of diametrically opposite notches and seats, each series comprising one notch individual to each said rod to receive the end thereof and a seat individual to each said heating element to receive a terminal with which the corresponding end of such heating element is provided, and a hearth member spaced from which said elements and rods are supported by said first mentioned means.

2. In an electric heating unit, the combination of a plurality of helically wound heating elements, an insulating rod individual to each said heating element, said insulating rods being passed axially through the corresponding heating elements, means for supporting said rods and elements so that said elements lie in a generally horizontal plane with the individual elements arranged substantially parallel to but laterally spaced from each other, said supporting means comprising an insulating supporting member common to all said elements and rods, said member having a plurality of notches cut therein, each said notch being formed to receive and support the end of a corresponding rod, said member having a plurality of seats formed thereon one individual to each said heating element and adapted to receive a terminal with which the corresponding end of each such heating element is provided, and an upwardly presenting cuplike casing having an interior reflecting surface for receiving and supporting the aforesaid supporting means.

3. In an electric heating unit, the combination of a plurality of helically wound heating elements, an insulating rod individual to each said heating element, said insulating rods being passed axially through the corresponding heating elements, means for supporting said rods and elements so that said elements lie in a generally horizontal plane with the individual elements ing element is provided, an upwardly presenting cuplike casing having an interior reflecting surface for receiving and supporting the aforesaid supporting means, and means comprising terminal studs passed through said casing and said insulating supporting member for securing said supporting member to said casing and for electrically connecting said heating elements to an external supply circuit.

JAMES ISBISTER. 

